1. Field of the Invention
The present invention relates to a pigment dispersion liquid, an ink jet recording ink (hereinbelow which may be referred to simply as “ink), an ink jet recording method, an ink cartridge and an ink jet recording apparatus. More particularly, the present invention relates to a pigment dispersion liquid of the coloring material dispersion type and an aqueous ink jet recording ink which have high storage stability, good fixation of printed images as well as fastness of recorded images and are suitable for ink jet recording, and to an ink jet recording method, an ink cartridge and an ink jet recording apparatus using the ink.
2. Description of the Related Art
Conventionally, water-insoluble coloring materials such as pigments excellent in fastness such as water fastness and light fastness have been widely used as a coloring agent for a printing ink. However, in order to use a water-insoluble coloring material as a coloring material for an aqueous ink, it is required to stably disperse the water-insoluble coloring material in an aqueous medium. Owing to this, aqueous inks of the coloring material dispersion type in which a water-insoluble coloring material is uniformly dispersed in an aqueous medium by adding a dispersant such as a polymer compound or a surfactant have been used.
In recent years, in applications to ink jet recording as well, such aqueous ink jet recording inks of the coloring material dispersion type have come to be used as inks in view of image fastness. Attempts to impart an aggregation function and a water insolubilization function to coloring material particles in the ink have been made in respect of ink jet recording in order to improve fixation of recorded images and water fastness of ink on paper. However, when the coloring material particles are provided with these functions, dispersion stability of the coloring material particles in the ink is deteriorated, the coloring material particles will aggregate during storage of the ink, which causes such problems that concentration unevenness and sedimentation are liable to occur, that drying of the ink at the tip of a nozzle of an ink jet apparatus causes clogging and thereby ejection stability of the ink is liable to deteriorate.
In order to solve the problems mentioned above, Japanese Patent Application Laid-Open No. H04-227668, Japanese Patent Application Laid-Open No. H05-179183 and Japanese Patent Application Laid-Open No. 2005-177756 propose block polymers having a particular acrylic monomer structure in a hydrophilic segment thereof, but affinity of the hydrophilic monomer structure region, which constitutes the polymer, to recording materials is insufficient in these polymers, and accordingly, when these polymers are used in ink, image fastness such as ink fixation and scratch resistance is not at a sufficiently satisfactory level. Furthermore, in uses for which long-term continuous printing is required in industrial applications, an ink containing a block polymer mentioned above has such a problem to be solved that the ejection stability of the ink is significantly deteriorated.
In the meantime, Japanese Patent Application Laid-Open No. 2006-282760 proposes an ink containing a polymer dispersant and an urethane resin, but this ink has such a problem that dispersion stability of the coloring material particles at the time of a long term storage or a storage at a high temperature is significantly deteriorated, and besides, ejection stability of the ink is significantly deteriorated in uses for which long-term continuous printing is required in industrial applications. In addition, when such an ink is used in an ink jet recording apparatus which causes the ink to fly by thermal energy, such a problem is caused that the coloring material particles severely aggregate to make it impossible to eject the ink.